Diatomaceous earth (DE) is a material predominately made up of the fossilized remains of diatoms, in particular the silica shell of diatoms known as a frustule, which are naturally occurring deposits characterized by lattice-like architectures. The physical structure of fossil diatoms includes numerous pores that give the material a very high surface pore volume and internal pore volume, contributing to the materials outstanding absorptive quality. DE is mined from sedimentary deposits and processed into a variety of grades useful in many applications. Such applications include filter material, abrasives, mechanical insecticide, cat litter, absorbents, chemical stabilizer (ex. nitroglycerin), and thermal insulator. Despite its many uses, there are constraints that limit the applicability of diatomaceous earth. For example, water borne applications are generally not practical. The material does not suspend in water or remain dispersed well enough for liquid spray application. Furthermore, prolonged storage in water results in compacted sediment that is difficult to re-suspend.
A well known use of DE is as a mechanical insecticide that kills numerous different crawling insects. It is generally accepted that when insects crawl over or through dry DE powder they will suffer physical damage to their waxy epicuticle, and then the absorptive quality of DE extracts lipids from the insects body, causing a lethal dehydration. Unfortunately, reliable application of DE to surfaces where insects often crawl can be difficult because DE does not easily suspend in water for spray applications, and application of dry powder DE does not allow for adequate coverage on vertical or overhead surfaces. DE is often applied by pressurized air, which creates nuisance dust. Unmodified DE has a high energy surface with numerous hydroxyl groups that hydrogen bond causing the material to become compact and claylike after settling in aqueous medium. There is a need for a DE that forms a suspension in water and has flow characteristics that make it amenable to spray application to all surfaces where insects cause problems.